Systematic implications of morphological traits variation and rbcL sequence polymorphism on inter-species relationships of the subtribe Plucheinae (tribe Inuleae - Asteraceae)

Abstract

The classification of species in the subtribe Placentae (Asteraceae) has been addressed based on variation in morphological traits and polymorphism in the rbcL sequence. Phylogenetic trees based on the morphological variation strongly support the differentiation of Tessaria integrifolia, Cylindrocline commersonii, Geigeria alata, Sphaeranthus suaveolens, and Sphaeranthus indicus, from a larger clade that encompasses all species of Pluchea this clade includes other species, such as Dittrichia viscosa and Pulicaria dysenterica, which serve as outgroup species within the subtribe Inulinae. The rbcL polymorphism demonstrated the separation of Dittrichia viscosa and Pulicaria dysenterica from the other Plucheinae species. Furthermore, it revealed the paraphyly of Pluchea and Laggera and the incorporation of Laggera alata and Tessaria integrifolia into the Pluchea clades. However, the rbcL data confirmed the current taxonomic position of most of the Plucheinae species at the genus level. The analysis of the combined rbcL sequence polymorphism and variations in the morphological traits produced a better resolution of examined species compared to the trees based on the analysis of the rbcL only. Heat maps illustrating the taxonomic relatedness of the studied species generally revealed results similar to those of the cluster trees and the PCA scatter diagrams. In conclusion, the rbcL sequences are helpful for the authentication and discrimination of Plucheinae species. However, the phylogenetic analysis of the rbcL barcode polymorphism revealed ambiguous taxonomic relationships among Plucheinae species and the taxonomic group's heterogeneity.